This invention relates to irrigation emitters and more particularly to an irrigation emitter providing pressure compensation so that flow rate remains substantially constant as input pressure varies.
Drip irrigation systems are used to deliver water and/or nutrients directly to the root zone of a plant. In use, an online emitter is inserted into the water lateral lines. The emitter thus acts as a point source for water. Because water is delivered in a controlled way, it is possible to irrigate with substantially less water as compared to conventional water delivery systems including sprinklers and flooding methods. Drip irrigation systems also experience less water percolation, surface run off or evaporation, all saving water. Other advantages are fewer weeds as water is applied only to regions where it is required. Less fertilizer is used as a result of the targeted watering and higher yields result from the better soil moisture levels.
As water in drip irrigation systems travels through a pipe network including a sub main and lateral pipes from a water source out to a field, there is a continuous pressure loss due to frictional forces that develop between the pipe and flowing water. Other factors such as elevation can also result in water pressure variation. If non-pressure compensating emitters are used, the emitters subject to higher pressures will emit more water, leading to an uneven water distribution in the field. Plants closer to the water and pumping source get more water than the ones farther away. It is desirable that all emitters have uniform water flow rates along the lateral lines.
Pressure-compensating emitters have been developed that emit constant flow rate of water despite a fluctuation in input water pressure. Such pressure-compensating emitters thus enable longer lateral pipes to be used so that a larger area can be irrigated with the drip irrigation system.
Existing pressure-compensating emitters have a relatively high activation pressure and a limited operating range. Activation pressure is defined as the pressure above which an emitter begins pressure compensation. Because pumping power in an irrigation system is a function of the water pressure and its flow rate, a high activation pressure means higher power requirements leading to higher incurred costs in power systems, pumps and the need for thicker pipes.
Many of the currently manufactured pressure-compensating emitters are derivatives of a dripper patented in 1949 as U.S. Pat. No. 2,460,647. The Jain Irrigation Company is a major current-day pressure-compensating emitter manufacturer. Typical Jain Irrigation emitters have an activation pressure of 1.0 bar and an operating range of 3 bars in an 8 liter/hour dripper.
An object of the present invention is a pressure-compensating emitter that has a low activation pressure of around 0.15 bar and large operating range beyond 4 bars to ensure uniform water distribution on a large field. Another object of the invention is an iterative design procedure for designing pressure-compensating emitters with low activation pressure and larger operating range.